Mesothelioma

Mesothelioma

 

Mesothelioma is a rare malignancy involving the serous lining of body cavities (pleura, peritoneum, pericardium or tunica vaginalis testis).

Epidemiology

  • Incidence
    • 2500-3000 new cases annually in the U.S.
    • Occurrence is rising in males ≥75 years old; however, it is not in males and females <75 years old (coincides with OSHA restrictions of permissible limits of asbestos exposure)
    • Maximum lifetime risk in 1925-1929 birth cohort
  • Age – peak age 40-60 years
  • Gender – strong male predominance

Risk factors

  • Asbestos exposure (amphiboles more carcinogenic than chrysotile fibers)
    • 80% of mesothelioma cases occur in patients with history of asbestos exposure
    • At-risk occupations include shipbuilding, construction, fireproofing, automobile brakes and clutches, ceiling tiles, boilers (especially in construction prior to 1970)
  • Genetics
    • Chromosome deletions (1p, 3p, 9p, 6q)

Clinical presentation

  • Pleural
    • Dyspnea, nonpleuritic chest pain, pleural effusion, cough, fatigue
  • Peritoneal
    • Abdominal pain, ascites
  • Pericardial
    • Chest pain, constrictive pericarditis
  • Disease process is usually advanced at time of presentation

Pathophysiology

  • 3 types of malignant mesothelioma
    • Epithelial – 50%
    • Sarcomatous – 15%
    • Biphasic (or mixed) – 25%
  • May be mistaken for adenocarcinoma
  • Long latency period (>20 yrs) between asbestos exposure and development of mesothelioma
  • Asbestos fibers are mutagenic and carcinogenic to several cells
    • Commonly found in excised tumors

Diagnosis

  • Indication for testing
    • High suspicion including abnormal chest X-ray (pleural effusion, pleural plaques) and history of asbestos exposure
  • Laboratory testing
    • Tissue specimen for histology (using special stains)
      • Body cavity fluid cytology – may be negative
        • Not all patients with mesothelioma develop effusions
      • Pleural biopsy – CT guided or thorascopic biopsy
      • Open thoracotomy – last resort
    • Serum testing is not useful
  • Imaging
    • CT/MRI for initial evaluation of abnormal chest X-ray

Disease monitoring

  • Soluble mesothelial-related peptide testing
    • Useful for monitoring epithelial or biphasic mesothelioma
    • Requires serial measurement
    • Not useful as a diagnostic test

See Also